Field of the Invention
The present invention relates to a resist under layer film composition for fine patterning in a manufacturing process of a semiconductor apparatus and the like, and to a patterning process.
Description of the Related Art
In recent years, double patterning which includes repeating lithography and etching steps (LELE, Litho-Etch-Litho-Etch) has been used to form interconnect with high density by three-dimensional gate such as ultra-fine and dense Fin-field effect transistor (Fin-FET) or dual damascene, in which trenches and vias of copper interconnect are formed at the same time. Accordingly, materials capable of filling gaps with high aspect ratio and high density have been demanded. Filling gaps makes the film surface flatten and facilitates focus leveling in lithography, thus enabling patterning with an adequate margin even if the focus margin is narrow.
A spin coating method has been commonly used for planarizing a substrate having gaps. Otherwise, the gaps can be filled by forming an amorphous carbon film by chemical vapor deposition (CVD) method, but this method has a disadvantage of process cost because the surface becomes uneven and the film surface is required to be ground by chemical mechanical polishing (CMP) method to planarize it. Moreover, there is a problem that the amorphous carbon film formed by the CVD method fails to fill ultra-fine gaps with a pitch of 50 nm or less because voids occur in the bottom of the gaps. The ultra-fine gaps with a pitch of 50 nm or less can be filled by spin coating of a material containing a large amount of low molecular weight components.
A liquid immersion lithography makes an angle of incident light to a resist and an underlying layer(s) shallower and substrate reflection larger. To suppress the substrate reflection, a multi-layer antireflection film is effectively formed under the resist. A 3-layer (tri-layer) structure in which a hydrocarbon film (a resist under layer film) with high carbon density is formed on a substrate, a silicon-containing resist middle layer film is formed thereon, and a resist upper layer film is formed thereon can prevent the substrate reflection by the two layers of the hydrocarbon film and the silicon-containing middle layer film. Thus, the application of this technique has been rapidly spreading with use of the liquid immersion lithography.
The resist under layer film is required to have functions such as filling and planarizing properties by spin coating, high dry-etching resistance for dry etching a substrate, and optimum optical properties for providing high antireflection effect.
The resist under layer film is also required to have high heat resistance in some cases, for example, when a hard mask layer such as p-Si, SiN, SiON, TiN, ZrO2, and HfO2 is formed on the resist under layer film because these films need a temperature exceeding 300° C. to be formed.
Examples of a resist under layer film material with high heat resistance include a bisnaphthol compound and a novolak resin thereof disclosed in Patent Document 1, bisnaphthol fluorene and a novolak resin thereof disclosed in Patent Document 2, a novolak resin of naphthol phthalein disclosed in Patent Document 3, and a novolak resin of naphthofluorescein disclosed in Patent Document 4.
In addition, there is a problem of outgas generated in baking for forming a resist under layer film. The outgas component adheres to an upper plate above a hot plate, and when the component drops onto a wafer, a defect is generated. To improve the property of filling gaps of a substrate, monomer components (low molecular weight components) are effectively added to the resist under layer film composition. However, the more the monomer components are added, the more outgas is generated in baking at high temperature. In other words, there is a trade-off relationship between the improvement in filling property and the reduction in outgas. Therefore, a resist under layer film composition that can overcome the trade-off relationship has been demanded.